FIG. 2.

Screening Tn916 insertional mutants of S. gordonii Challis in agar plate bacteriocin assays. S. mutans GS5 alone or in mixtures with S. gordonii Challis or with S. gordonii Challis mutant 41A9 were inoculated into THB agar plates. After 24 h of incubation at 37°C under anaerobic conditions, the plates were overlaid with indicator RP66 cells (10⁶ CFU) in 3 ml of THB with 1% low-melting-point agarose. After 24 more hours of incubation at 37°C under anaerobic conditions, the diameters of the clearance zones surrounding the inoculated bacteria were measured. Zones: 1, S. mutans GS5 alone; 2, mixture of wild-type S. gordonii Challis and S. mutans GS5; and 3, mixture of S. gordonii Challis mutant 41A9 and S. mutans GS5.